Vitalight Mini CO2 Detector, Air Quality Monitor, Stylish and Lightweight CO2 Monitor You Can Use Anywhere.

This is the least intuitive piece of electronics I've ever used. I hate it. All the reviews about battery life sucking are correct. The problems with turning it off are correct. The only way to get any use out of it is to keep it plugged in, and unplug when you need it. Then pray you can get it turned off again, or that pressing twice will turn off the alarm so the damn thing doesn't start randomly beeping.3 stars because I have used it to make sure apartments are fully aired out after workmen have been here, otherwise it's be 1 star for the irritation factor alone.I wish I'd returned it immediately, I'm past the return period so the most I can do is save someone else the hassle.Guaranteed that some day I will get so irritated with this thing I'll stomp on it in my winter boots.Seriously. Don't buy it.It could have been a nice little monitor, with a couple of extra buttons - an on/off switch for the device - with an indicator that shows whether it's off or on, and the alarm.Oh, didn't I mention that? The screen goes dark when it's ON, and when it's off. How do you know the difference? You don't!

I love this device but highly recommend reading the Breathe Safe Air review before purchase. This is a really great value and I trust the readings based on the BSA review and the ways it responds to changes in the environment. I got this to gauge ventilation levels as a proxy for covid-19 risk in public spaces and it works very well for this. Lightweight, small, portable, not very conspicuous, gives quick readings (about 30 seconds). It’s given me some really useful info on safety levels at various places I frequent, as well as good data on when I need to increase ventilation in my home office and bedroom. I found the controls really easy to use and learn. The screen goes blank to save battery but a short press on the button will quickly tell you if it’s on or off. Long press to both turn on and turn off. Double press to turn sound on and off. That’s pretty much it. Calibration has a complex set of commands you need the reference instructions for but that’s common with these types of devices. Battery life is pretty good, but I don’t need it to be on constantly.Here are the downsides (to me, minor annoyances, but could be dealbreakers to some):- Sound is on by default even if you muted it the last time it was on. Easy to mute but need to remember to do so if you don’t want annoying beeping any time the levels go above 1000.- Turning it off causes a short beep even if sound is muted.- The BSA goes into this in depth, but the autocalibration feature can cause misreadings over time if you’re not careful. Pretty easy to avoid by either taking the device outside while it’s on at least once a week or recalibrating it outside a few times.- The screen is hard to read outside due to glare. I don’t really need it for outside readings, so not a huge deal for me.The price is many times lower than other devices that have similar accuracy levels, so it’s definitely worth the tradeoffs to me.

UPDATE: I messaged the seller and they sent me a new one within a day. I've had the new one running for 2 weeks now and it works great! So I think this is confirmed, the first one was just a dud. I'll update this review if the new one breaks anytime soon. Readings have seemed very accurate based on how my home is overnight and then with windows open. I've taken it a few places and the readings continue to seem right.Also sounds like everyone is having a hard time using this thing? Press and hold to turn on/off. Once it's on, double click the button to turn off beeping. The battery isnt phenomenal but works for the day, I keep mine plugged into a USB while at home and unplug when I head outI really wanted to love it but after a day or so the readings become wildly inaccurate, regardless of re-calibration. Not sure if I got a defective one but the screen mostly reads as ERR or 4000+, even when outside. I’ve recalibrated so many times outside and it continues to read the same issues after. I’ve learned if I just leave it plugged in on my counter it will eventually go back to functioning after about 48 hours… only to ERR and break again a few days later. And of course it’s been errored out every time I’ve tried to take it out with me somewhere… But when it DOES decide to work, it’s fantastic. I hope the seller sees this and issues me a new one, really hoping it’s just a dud.

Out of the box, my Vitalight consistently read at least 100ppm lower than an Aranet4 and another monitor based on a Sensirion SCD-41. The outdoors calibration routine did not help much, possibly because it is programmed to equate outdoors CO2 with 400ppm, as opposed to ~420-450 in my small city. A trick that seemed to help, if you have an old-school gas range: put it on the counter beside the range and fire up all the burners. Leave it there for about 5 minutes WITHOUT the hood running, which will drive the ambient CO2 up into the 1000-1200ppm range. Afterwards, my Vitalight was within 50ppm of an Aranet4, which matches the outdoors calibration error/bias. If no gas you can also probably just take it for a windows-up, recirculated air drive, which will push the CO2 in your car way up inside of 20-30 minutes. TBD whether the Vitalight drifts out of calibration again...

I have a few minor complaints. First is the calibration process involves pressing the power button in just the right sequence. I'd prefer a separate button. It also lacks a high and low PPM display. For example I'd like to see how high the CO2 goes in our house overnight or over a work day in my office.The battery looks like it will last about 24 hours when new. I would prefer some control over how long the display stays on. I'd also like the display to stay on continuously when plugged into the USB port.It did charge off of my phone's USB-C charger cord last night.Overall nice size, easy to use, and accurate enough. This review is a mere 24 hours after I opened the device. I'll report back if it fails.